Method and apparatus for controlling a temperature of a polishing pad used in planarizing substrates

ABSTRACT

A method and apparatus for controlling a polishing characteristic of a polishing pad used in planarization of a substrate. The method preferably includes controlling the temperature of a planarizing surface of the polishing pad so that waste matter accumulations on the planarizing surface soften and/or become more soluble, and/or material comprising the planarizing surface attains approximately its glass transition temperature. The waste matter accumulations and/or a portion of the planarizing surface are in this way softened and more easily removed. The planarizing surface is either heated directly by directing a flow of heated planarizing liquid or heated air to the planarizing surface or indirectly by heating a support surface beneath the polishing pad or by heating the air proximate to the polishing pad.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/338,030, filed Jun. 22, 1999 now U.S. Pat. No. 6,533,647, which is acontinuation of U.S. patent application Ser. No. 08/993,256, filed Dec.18, 1997, issued Sep. 28, 1999, as U.S. Pat. No. 5,957,750.

TECHNICAL FIELD

The present invention relates to methods and apparatus for conditioningof polishing pads used in planarizing substrates.

BACKGROUND OF THE INVENTION

Chemical-mechanical planarization (“CMP”) processes remove material fromthe surface of semiconductor wafers or other substrates in theproduction of microelectronic devices and other products. CMP processestypically planarize and/or polish the surface of the substrate in thefabrication of integrated circuits by moving the substrate across apolishing medium to remove material from the substrate surface.

FIG. 1 is a schematic view that illustrates a conventional CMP machine10 with a platen 20, a wafer carrier 30, a polishing pad 40, and aplanarizing liquid 44 on the polishing pad 40. The platen 20 istypically connected to a drive assembly 26 to rotate the platen 20(indicated by arrow A) or reciprocate the platen 20 back and forth(indicated by arrow B). Additionally, the wafer carrier 30 generally hasa lower surface 32 to which one or more wafers 12 may be attached, orthe wafers 12 may be attached to resilient pads 34 positioned betweenthe wafers and the lower surface 32. The wafer carrier 30 is generallyattached to an actuator assembly 36 to impart axial and/or rotationalmotion to the wafers 12 (indicated by arrows C and D, respectively), orthe wafer carrier 30 may be a weighted, free-floating wafer holder (notshown).

The polishing pad 40 and the planarizing liquid 44 may separately, or incombination, define a polishing medium that mechanically and/orchemically removes material from the surface of a wafer. The polishingpad 40 may be a conventional polishing pad made from a continuous phasematrix material (e.g., polyurethane), or it may be a new generationabrasive polishing pad made from abrasive particles fixedly dispersed ina suspension medium. Conversely, the planarizing liquid 44 may be aconventional CMP slurry with abrasive particles, or it may be aplanarizing solution without abrasive particles. In general, abrasiveslurries are used with conventional non-abrasive polishing pads andplanarizing solutions are used with abrasive polishing pads.

To planarize the wafers 12 with the CMP machine 10, the wafer carrier 30presses the wafers 12 face-downward against the polishing medium. Morespecifically, the wafer carrier 30 generally presses the wafers 12against the planarizing liquid 44 on a planarizing surface 42 of thepolishing pad 40, and at least one of the platen 20 or the wafer carrier30 moves relative to the other to move the wafers 12 across theplanarizing surface 42. As the wafers 12 move across the planarizingsurface 42, material is removed from the face of the wafers. The processis conventionally conducted at platen temperatures of approximately 85°F. to 105° F. to facilitate any chemical interaction between thepolishing medium and the wafer 12. Conventional wisdom is thatprocessing at higher temperatures may cause undesirable chemicalinteractions between the polishing medium and the wafer 12. Furthermore,where ammonia-based slurries are used, higher temperatures may cause theammonia to evaporate, creating undesirable odors and potentiallyshifting the pH of the slurry by an unacceptable amount.

In the competitive semiconductor industry, it is desirable to maximizethe through-put of finished wafers and to produce a uniform, planarsurface on each wafer. The through-put of CMP processing is a functionof several factors, one of which is the rate at which the thickness ofthe wafer decreases as it is being planarized (the “polishing rate”).The polishing rate affects the through-put because the polishing periodper wafer decreases with increasing polishing rates and it is easier toaccurately endpoint CMP processing with a consistent polishing rate.Thus, it is desirable to have a high, consistent polishing rate.

One manufacturing concern with CMP processing is that the through-putmay drop because the act of planarizing wafers alters the condition ofthe polishing pads. More specifically, slurry and particles from thewafer and pad build up on the planarizing surface of the polishing padand form waste matter accumulations that may cover portions of theplanarizing surface. The accumulations may take the form of a hard glazecoating on the planarizing surface which reduces contact between thewafer and the planarizing surface. The polishing rate accordinglychanges during CMP processing, which may make it more difficult toquickly planarize a wafer or endpoint the CMP process. Thus, the wastematter accumulations may reduce the through-put of CMP processing.

CMP processes must also consistently and accurately produce a uniform,planar surface on the wafer because it is important to accurately focusthe image of circuit patterns on the surface of the wafer. As thedensity of integrated circuits increases, it is often necessary toaccurately focus the critical dimensions of the circuit pattern towithin a tolerance of approximately 0.1 μm. Focusing circuit patterns tosuch small tolerances, however, is very difficult when the surface ofthe wafer is not uniformly planar. Thus, planarizing processes mustcreate a highly uniform, planar surface.

Another problem with CNP processing is that the waste matteraccumulations reduce the uniformity of the polishing rate across theplanarizing surface of a polishing pad. The waste matter accumulationsdo not build up uniformly across the planarizing surface of thepolishing pad, and thus the polishing rate may vary unpredictably acrossthe polishing pad. As a result, the surface of a polished wafer may notbe uniformly planar.

The problems associated with waste matter accumulations are exacerbatedwhen the planarizing surface simultaneously planarizes a large number ofwafers or when the planarization rate is increased. For example, FIG. 1illustrates a single wafer carrier 30 to which are attached severalwafers 12, each of which contributes waste matter accumulations to theplanarizing surface. In other conventional CMP machines, multiple wafercarriers, each with multiple wafers, further increase the rate at whichwaste matter accumulates on the planarizing surface. As the number ofwafers planarized by a given planarizing surface increases, the rate atwhich waste matter accumulates on the planarizing surface alsoincreases, decreasing wafer through-put and wafer uniformity.

In light of the problems associated with waste matter accumulations onpolishing pads, it is necessary to periodically remove the waste matteraccumulations from the planarizing surfaces so that the polishing padsare brought back into a desired state for planarizing substrates(“conditioning”). For example, U.S. Pat. No. 5,456,627 issued to Jacksonet al. discloses an apparatus for conditioning a rotating, circularpolishing pad with a rotating end effector that has an abrasion disk incontact with a polishing surface of the pad. The end effector describedin U.S. Pat. No. 5,456,627 moves along a radius of the polishing padsurface at a variable velocity to compensate for the linear velocity ofthe polishing pad surface. Additionally. U.S. Pat. No. 5,456,627discloses maintaining a desired contact force between the end effectorand the polishing pad surface with a closed feedback loop in which aload transducer generates a signal with an amplitude proportional to theapplied force. A computer then uses the signal from the load transducerto operate an actuator that moves the end effector in a direction sothat the output of the load transducer is substantially equal to thedesired contact force.

Another conventional conditioning method and apparatus, which isdisclosed in U.S. Pat. No. 5,081,051 issued to Mattingly et al., uses anelongated blade with a serrated edge that is engaged with a portion of acircular, rotating polishing pad. The blade disclosed in U.S. Pat. No.5,081,051 is pressed against a polishing path on the planarizing surfaceof the polishing pad to scrape or cut grooves into the planarizingsurface.

Conventional conditioning methods and devices, however, take time tocondition the pad because they abrasively wear away or cut through wastematter accumulations which have formed a hardened glaze on theplanarizing surface. Additionally, conventional conditioning methods anddevices may result in a non-planar surface on the polishing pads.Therefore, it would be desirable to develop a method and apparatus thatreduces the time required to condition the polishing pads and improvesthe quality of the conditioned pads.

SUMMARY OF THE INVENTION

The present invention is directed, in part, toward a method andapparatus for controlling a polishing characteristic of a polishing padused in planarization of a substrate. In one embodiment of the method,the temperature of a planarizing surface of the polishing pad iscontrolled to be at least approximately 98% of a glass transitiontemperature of polishing pad material comprising the polishing pad. Themethod further comprises removing material from the planarizing surface.The method may further comprise removing a predetermined thickness ofthe polishing pad to further control the polishing characteristic of thepolishing pad. In one embodiment of the invention, the temperature ofthe planarizing surface is controlled by electrically heating a supportsurface supporting the polishing pad. In an alternate embodiment, theplanarization surface is positioned within an insulated enclosure and isheated by heating the air within the enclosure proximate to theplanarizing surface. In further alternate embodiments of the invention,the planarizing surface is heated directly. In one such embodiment,heated air is directed toward the planarizing surface. In another suchembodiment, a heated planarizing liquid is directed toward theplanarizing surface. The heated planarizing liquid both heats theplanarizing surface and the waste matter accumulations thereon and, inone embodiment, aids in chemically-mechanically planarizing thesubstrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a planarizing machine inaccordance with the prior art.

FIG. 2 is a partial cross-sectional view of an embodiment of aplanarizing machine in accordance with the invention having a heatedplaten.

FIG. 3 is a partial cross-sectional view of another embodiment of aplanarizing machine in accordance with the invention having a heated,insulated enclosure.

FIG. 4 is a partial cross-sectional view of another embodiment of aplanarizing machine in accordance with the invention in which a flow ofheated planarizing liquid is directed toward a planarizing surface of apolishing pad.

FIG. 5 is a partial cross-sectional view of another embodiment of aplanarizing machine in accordance with the invention in which a flow ofheated air is directed toward a planarizing surface of a polishing pad.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a heated planarizing surface of a polishing padfor planarizing semiconductor wafers, base plates for field emissiondisplays, and other related substrates. An important aspect of theinvention is that the planarizing surface of the polishing pad ismaintained at a predetermined temperature while the pad is conditioned.Thus, unlike unheated polishing pads, a glaze layer which forms on thepad during CMP processing may be softened and easily removed duringconditioning to increase the uniformity of the conditioned pad andreduce the time required to condition the pad. FIGS. 2-5 illustratevarious embodiments of heating methods and apparatus, and like referencenumbers refer to like parts throughout the various figures.

FIG. 2 is a partial cross-sectional view of a planarizing machine 200 inaccordance with an embodiment of the present invention having a heatedplaten 220. The platen 220 supports a polishing pad 240 which has aplanarizing surface 242 opposite the platen. The planarizing surface 242engages wafers or other substrates 212. Material is removed from thesubstrates 212 by motion of the platen 220 and the substrates 212relative to each other.

The substrates 212 are engaged and held in place against the planarizingsurface 242 by a wafer carrier 230 and a resilient pad 234. In oneembodiment, two wafer carriers 230 each engage three substrates 212, asshown in FIG. 2. In alternate embodiments, a greater or lesser number ofwafer carriers 230 engages a greater or lesser number of substrates 212.

In one embodiment of the invention, the wafer carriers 230 each havecarrier actuators 236 connected to a carrier manifold 231. The carrieractuators 236 may cause the wafer carriers 230 to reciprocate (indicatedby arrow E′) and/or rotate (indicated by arrow F′) so as to generate arelative motion between the substrates 212 and the planarizing surface242. The carrier manifold 231 is in turn connected to a manifoldactuator 235. The manifold actuator causes the carrier manifold 231 toreciprocate (indicated by arrow C′) and/or rotate (indicated by arrowD′) so as to generate additional relative motion between the substrates212 and the planarizing surface 242. The additional relative motionbetween the substrate 212 and the planarizing surface 242 increases therate at which the substrate 212 is planarized. Further additionalrelative motion between the substrate 212 and the planarizing surface242 may be generated by translating and/or rotating the platen 220 witha platen drive assembly 226 as indicated by arrows B′ and A′,respectively. Alternate embodiments of the planarizing machine 200incorporate other arrangements for generating relative motion betweenthe substrate 212 and the planarizing surface 242.

The planarizing rate of the substrates 212 may be further increased inthe embodiment shown in FIG. 2 by adding a planarizing liquid 244 to theplanarizing surface 242. As shown in FIG. 2, a liquid conduit 260supplies the planarizing liquid 244 directly to the planarizing surface242. The planarizing liquid 244 may be a planarizing solution having noadditives, or it may be a slurry having abrasives and/or chemical agentsthat aid in mechanically and/or chemically removing material from thesurfaces of the substrates 212. One such slurry includes anammonia-based compound to increase the planarization rate. Theplanarizing liquid 244 has other compositions in other embodiments. Theplanarizing liquid 244 and the polishing pad 240 may separately or incombination define a polishing medium that mechanically and/orchemically removes material from the surface of the substrates 212 asthe substrates move relative to the planarizing surface 242.

During planarization of the substrates 212, particles abraded from thesubstrate as well as other materials such as the planarizing liquid 244,form waste matter accumulations 264 which vary in thickness across theplanarizing surface 242. Over time, the waste matter accumulations 264tend to harden into a glaze layer which is interposed between theplanarizing surface 242 and the substrates 212, reducing contact betweenthe planarizing surface and the substrates, and therefore reducing therate at which the planarizing surface planarizes the substrates. Therate at which the waste matter accumulations 264 form and harden isbelieved to be a function, in part, of (1) the relative velocity betweenthe substrates 212 and the planarizing surface 242; (2) the number andsize of substrates 212 in contact with the planarizing surface 242; and(3) the presence of soft doping materials such as polysilicon in thesubstrates 212.

To increase the through-put of finished substrates, it is desirable toincrease the relative velocity between the substrates 212 and theplanarizing surface 242, and to increase the number of substratesplanarized at any one time. It is also desirable to planarize substrates212 containing doping materials. However, as mentioned above, each ofthese processes tends to increase the rate at which waste matteraccumulations 264 form on the planarizing surface 242 and decrease theplanarizing rate of the substrates 212. Therefore, the glazed wastematter accumulations 264 are a significant problem in CMP processing.

To remove the waste matter accumulations 264 from the polishing pad 240and restore the polishing characteristics and effectiveness of theplanarizing surface 242, the polishing pad is conditioned with aconditioning disk 250, either concurrently with the planarizationoperation discussed above, or in a separate step. In one embodiment, theconditioning disk 250 has a conditioning surface 251 which contacts theplanarizing surface 242 during conditioning. The conditioning disk 250is connected to a conditioning disk actuator 252 which imparts arotational and/or translational motion to the conditioning disk 250(indicated by arrows G′ and H′, respectively) and causes theconditioning disk to move relative to the polishing pad 240. In thisway, the conditioning surface 251 of the conditioning disk 250 abradesor cuts the waste matter accumulations 264 as it moves over theplanarizing surface 242 and also removes a selected amount of materialfrom the polishing pad 240.

In one embodiment in which the polishing pad 240 is a polyurethane-basedIC-1000 pad manufactured by Rodel Corp. of Newark, N.J., the thicknessof material removed from the polishing pad, not including the thicknessof any waste matter accumulations 264, is in the range of approximately0.00099 mm to approximately 0.003 mm per conditioning cycle. Theplanarizing characteristics of the polishing pad 240 are substantiallyrestored by removing the waste matter accumulations 264 and a thicknessof the pad material within the range indicated above. Other thicknessesof pad material may be removed from other types of polishing pads 240during conditioning.

In one embodiment, the conditioning operation is expedited by supplyingthe planarizing liquid 244 to the planarizing surface 242 duringconditioning. The planarizing liquid 244, which may be a slurry,augments the conditioning disk 250 by chemically, chemically etching,and/or mechanically removing material from the polishing pad 240.

To further increase the speed and uniformity with which waste matteraccumulations 264 are removed from the planarizing surface 242, theplanarizing surface is heated to a selected temperature with atemperature controller. In the embodiment shown in FIG. 2, thetemperature controller comprises an electrical heating element 270positioned within the platen 220. The platen 220 heats up whenelectrical current is passed through the heating element 270. Byconduction, the heated platen 220 heats the polishing pad 240 and, inparticular, the planarizing surface 242 of the polishing pad and thewaste matter accumulations 264 on the planarizing surface. In analternate embodiment, the heating element 270 is positioned within thepolishing pad 240 itself to more directly heat the planarizing surface242. In a further alternate embodiment, the heating element ispositioned within the conditioning disk 250 to heat the planarizingsurface 242.

The heating element 270 is electrically coupled to a power supply 276which supplies electrical power thereto. In the embodiment shown in FIG.2, the heating element 270 is connected with leads 271 to circularcontact rings 272 a and 272 b which extend around the outer periphery ofthe platen 220. The contact rings 272 a and 272 b slideably engagecontacts 274 a and 274 b, respectively, which are connected withelectrical leads 275 to the power supply 276 in a conventional manner.When the platen 220 rotates, the contact rings 272 a and 272 b maintainengagement with the contacts 274 a and 274 b to continuously supplypower to the heating element 270. In other embodiments, other devicesmay be used to supply power from the stationary power supply 276 to themovable heating element 270.

In one embodiment, the heating element 270 is actuated to heat the wastematter accumulations 264 to a selected temperature. At the selectedtemperature, the waste matter accumulations 264 soften and become lessviscous and are therefore easier to remove from the planarizing surface242. The waste matter accumulations 264 may also become more soluble inthe planarizing liquid 244 at the selected temperature, furtherincreasing the rate at which the waste matter accumulations may beremoved from the planarizing surface 242. The effect has been observedfor substrates which have been doped with soft doping materials such aspolysilicon and is accordingly advantageous because the soft dopingmaterials may be more likely than harder materials to form waste matteraccumulations. Furthermore, the heating element may be actuated to heatthe polishing pad 240 so that material comprising the polishing padattains a temperature at the planarizing surface 242 which is believedto be approximately its glass transition temperature, causing thepolishing pad material to soften and become easier to remove.Additionally, as the polishing pad material softens, it may becomeeasier to remove the waste matter accumulations 264 therefrom.

In one embodiment, wherein the polishing pad 240 is an IC-1000 whichcomprises polyurethane and is manufactured by Rodel Corp. of Newark,N.J., the polishing pad material has a glass transition temperature ofapproximately 100° F. (311° K). The planarizing surface 242 is heated toa temperature in the range of approximately 90° F. (305° K) toapproximately 115° F. (319° K) and preferably approximately 100° F.(311° K) to heat the polishing pad 240 and the waste matteraccumulations 264 thereon. Accordingly, the planarizing surface 242 isheated to a temperature in the range of approximately 98% toapproximately 103% of the glass transition temperature of the polishingpad material, as measured on an absolute temperature scale. In anotherembodiment, the platen 20 is heated to a temperature within the range ofapproximately 120° F. (322° K) to approximately 130° F. (328° K), whichis well beyond the conventional platen heating range of 85° F. to 105°F. and which causes the planarizing surface 242 to be heated to atemperature in the range of approximately 90° F. to approximately 115°F. In further embodiments, other planarizing surface and/or platentemperatures are used, depending on the composition and heat transfercharacteristics of the polishing pad 240, the platen 220, and the wastematter accumulations 264. For example, higher temperatures may be usedwhere the polishing pad 240 is thermally less conductive or has a higherglass transition temperature.

In one embodiment, the temperature of the planarizing surface 242 ismeasured with a temperature sensor 278. The temperature sensor 278 mayinclude an infrared sensor that directly measures the temperature of theplanarizing surface 242, or may include other sensing devices known inthe art. In one embodiment, a user may monitor the output of thetemperature sensor 278 and manually control the temperature of theplanarizing surface 242 to be within a desired range.

In an embodiment shown in FIG. 2, the temperature sensor 278 is coupledwith a lead 279 to a thermostat 280. The thermostat 280 is in turncoupled to the power supply 276 with a lead 281 to automatically controlpower to the heating element 270 and establish the desired temperatureat the planarizing surface 242 based on an input temperature receivedfrom the temperature sensor 278. The thermostat 280 may be set in aconventional manner to keep the planarization surface 242 at at leastapproximately 98% of its glass transition temperature and/or at atemperature at which the waste matter accumulations 264 soften and/orbecome more soluble. The thermostat setting may be adjusted dependingupon the heat transfer characteristics of the platen 220, polishing pad240 and/or waste matter accumulations 264.

Where conditioning occurs concurrently with planarization, as shown inFIG. 2, through-put is increased because the planarizing machine 200 mayeliminate waste matter accumulations 264 as they form, and therefore thewaste matter accumulations have a less substantial impact on theeffectiveness of the polishing surface 242. In one embodiment, the wastematter accumulations 264 may not form at all, and the relative motionbetween the polishing pad 240 and the substrates 212 may be sufficientto condition the polishing pad, reducing or eliminating the need for theconditioning disk 250.

Where conditioning and planarization are sequential, the through-put maybe increased by decreasing the amount of time required for conditioningand therefore decreasing the down-time of the planarizing machine 200.Where a slurry is used during conditioning, heating the planarizingsurface 242 may soften the waste matter accumulations 264 and/or thepolishing pad 240, thereby reducing the need for abrasive or chemicallyactive slurries. Instead, de-ionized water, which does not containexpensive abrasive or chemical additives, may be used duringconditioning resulting in additional cost savings.

A further advantage of the planarizing machine 200 is that by removingwaste matter accumulations 264 quickly, the effect of anynon-uniformities in the thickness of the waste matter accumulations isreduced. This is particularly so where conditioning and planarizationare simultaneous because the waste matter has less time to formsignificant accumulations and therefore less time to become non-uniform.

FIG. 3 is a partial cross-sectional view of another embodiment of aplanarizing machine 300 housed in an insulated enclosure 382. Theinsulated enclosure 382 substantially surrounds the platen 220, thepolishing pad 240, and the substrates 212 so as to minimize the heattransfer away from these components. Walls 384 of the insulatedenclosure 382 are preferably formed from a material having a low thermalconductivity so that the temperature within the insulated enclosure maybe easily regulated.

The temperature within the insulated enclosure 382 is regulated by atemperature controller comprising electrical heating elements 270 a, asshown in FIG. 3. In a preferred embodiment, a plurality of heatingelements 270 a may be used to uniformly heat the environment within theinsulated enclosure 382, as shown in FIG. 3. In an alternate embodiment(not shown), a single heating element 270 a may be centrally positionedwithin the insulated enclosure 382 or may extend around the periphery ofthe insulated enclosure to heat the interior of the insulated enclosure382. In further alternate embodiments, means other than electricalheating elements may be used to regulate the temperature within theinsulated enclosure 382.

The heating elements 270 a are capable of heating the environment withinthe insulated enclosure 382 and in particular, the planarizing surface242, to the point at which the waste matter accumulations 264 softenand/or become more soluble, and/or the material comprising the polishingpad 240 attains a temperature approximately equal to at least 98% of itsglass transition temperature. The heating elements 270 a are thereforepreferably positioned as close as possible to the planarizing surface242 without overheating other components within the insulated enclosure382 and without heating the planarizing surface non-uniformly orinterfering with the planarization operation.

The heating elements 270 a are coupled with the leads 275 to theelectrical power supply 276 in a conventional manner. In a preferredembodiment, the heating elements 270 a are automatically controlled bythe thermostat 280 which receives inputs from the temperature sensor278, in substantially the same manner as discussed previously withreference to FIG. 2. In this way, the temperature of the planarizingsurface 242 may be controlled to be within the range of approximately90° F.-115° F. in one embodiment. As discussed previously with referenceto FIG. 2, other temperature ranges may be used for other embodimentshaving different compositions of polishing pads 240 and/or waste matteraccumulations 264.

In one embodiment, the temperature sensor 278 may directly measure thetemperature of the planarizing surface 242. In another embodiment, thetemperature sensor 278 may measure other temperatures, such as the airtemperature within the enclosure 384, which are associated withcorresponding planarizing surface temperatures.

An advantage of the insulated enclosure 382 shown in FIG. 3, as comparedwith the heated platen 220 shown in FIG. 2, is that the insulatedenclosure does not require an electrical coupling between a movableheating element and a fixed power supply. This heated enclosure 382 istherefore less susceptible to mechanical failure during normal operationand is less likely to require maintenance or replacement. A furtheradvantage of the insulated enclosure 382 shown in FIG. 3 is that theenclosure is a simple and therefore low-cost construction and thecomponents that comprise the enclosure are easily available.

FIG. 4 is a partial cross-sectional view of another embodiment of aplanarizing machine 400 having a flow of heated planarizing liquid 244directed toward the planarizing surface 242 to control the temperaturethereof. The liquid conduit 260 has a conduit inlet 461 coupled to asupply vessel 476 containing heated planarizing liquid. A conduit nozzle462 is positioned above the planarizing surface 242 to direct theplanarizing liquid 244 onto the planarizing surface, heating thesurface. The temperature of the planarizing liquid 244 is regulated toheat the waste matter accumulations 264 on the planarizing surface 242to the point at which they soften and/or become more soluble in theplanarizing liquid 244, and/or to heat the material comprising thepolishing pad 240 to at least approximately 98% of its glass transitiontemperature. In this way, the waste matter accumulations 264 and/or padmaterial are more easily removed to condition the planarizing surface242. As discussed previously with reference to FIGS. 2-3, theplanarizing surface 242 may be heated to a temperature within the rangeof approximately 90° F. to 115° F., in one embodiment, and othertemperature ranges are used in other embodiments, depending upon thecomposition of the waste matter accumulations 264 and/or the polishingpad 240.

In one embodiment, the temperature of the planarizing surface isregulated automatically with the thermostat 280. The thermostat 280receives an input temperature signal from the temperature sensor 278 andcontrols the supply of planarizing liquid 244 delivered to theplanarizing surface 242 based on the difference, if any, between theinput temperature and the desired planarizing surface temperature. Inone embodiment, the thermostat 280 controls the temperature ofplanarizing liquid 244 by activating or deactivating a heat source 270 bwhich heats the planarizing liquid in the supply vessel 476. In anotherembodiment, the thermostat 280 controls the amount of planarizing liquid244 delivered to the planarizing surface 242 by opening or closing avalve 466 positioned in the liquid conduit 260.

In the embodiment shown in FIG. 4. a single liquid conduit 260 deliversthe planarizing fluid 244 to the planarizing surface 242 through asingle nozzle 462. In alternate embodiments (not shown), a plurality ofliquid conduits 260 or a liquid conduit having a plurality of nozzles462 may be used to more uniformly deliver planarizing liquid 244 to theplanarizing surface 242. In this way, the temperature of the planarizingsurface 242 and the waste matter accumulations 464 thereon may be moreuniformly elevated and controlled. In a further alternate embodiment,the polishing pad 240 may be thermally insulated from the platen 220 soas to reduce heat transfer away from the polishing pad which mightotherwise lower the temperature of the planarizing surface 242.

An advantage of the embodiment of the CMP machine shown in FIG. 4 isthat the planarizing surface 242 is heated directly. In this way, theamount of energy required to heat the waste matter accumulations 264and/or the planarizing surface 242 is reduced when compared to heatingthe platen 220 (FIG. 2) or the environment surrounding the platen (FIG.3). Another advantage is that by heating the planarizing surface 240directly, other components of the planarizing machine are notincidentally heated and are therefore less likely to fail as a result ofexposure to elevated temperatures. Yet another advantage of directlyheating the planarizing surface 242 is that the temperature of theplanarizing surface can be quickly changed because heating is confinedto the polishing pad. Rapid heating is advantageous particularly if theplanarizing surface is permitted to cool between conditioningoperations, because the time required to heat the planarizing surface242 prior to conditioning is reduced. A further advantage of theembodiment shown in FIG. 4 is that the liquid conduit 260 is an existingelement of typical CMP machines. Therefore, the effort and expenserequired to retrofit existing CMP machines with the capacity to elevatethe temperature of the polishing pad material and/or the waste matteraccumulations 264 thereon is reduced.

FIG. 5 is a partial cross-sectional view of another embodiment of aplanarizing machine 500 in accordance with the invention having a gasconduit 590 positioned to direct a flow of heated gas, such as air,toward the planarizing surface 242 to control the temperature thereof.The gas conduit 590 is connected at one end 591 to a heated gas source594. A nozzle 592 at an opposite end of the gas conduit 590 directs theflow of heated gas toward the planarizing surface, heating theplanarizing surface 242 and the waste matter accumulations 264 to atleast 98% of the glass transition temperature of the pad material. Atthis point, the waste matter accumulations 264 and/or pad materialssoften and become easier to remove, reducing the amount of time requiredto condition the polishing pad 240, as discussed previously withreference to FIGS. 2-4.

As discussed previously with reference to FIGS. 2-4, the temperature ofthe planarizing surface 242 may be regulated automatically with thethermostat 280. The thermostat 280 receives an input temperature signalfrom the temperature sensor 278 and adjusts the flow of gas delivered tothe planarizing surface based on any difference between the inputtemperature and the desired planarizing surface temperature. In oneembodiment, the thermostat 280 regulates the temperature of the gas flowby activating or deactivating a heating source 270 c which heats the gasin the gas source 594. In another embodiment, the thermostat 280controls the amount of gas delivered to the planarizing surface 242 byopening or closing a valve 596 positioned in the gas conduit 590.

In one embodiment a single gas conduit 590 delivers heated gas to asingle nozzle 591, as shown in FIG. 5. In alternate embodiments (notshown), a plurality of nozzles 591 coupled to a single gas conduit 590or coupled to a plurality of gas conduits direct heated gas to differentportions of the planarizing surface 242, uniformly heating theplanarizing surface and the waste matter accumulations 264 thereon. In apreferred embodiment, the gas comprises air, though in alternateembodiments, other gases may be employed to heat the planarizing surface242.

An advantage of the gas conduit 590 shown in FIG. 5 is that theplanarizing surface 242 and the waste matter accumulations 264 thereonare heated directly, reducing the time and energy required to heat theplanarizing surface and the waste matter accumulations 264, as discussedwith reference to the liquid conduit 260 of FIG. 4. An advantage of thegas conduit 590 when compared with the liquid conduit 260 is that thegas conduit 590 allows a user to control the temperature of theplanarizing surface 242 independent of the amount of planarizing liquid244 delivered to the planarizing surface. This is advantageous becauseit allows the user to change the rate at which the planarizing liquid244 is delivered to the planarizing surface 242 without substantiallychanging the temperature of the planarizing surface. In this way, theplanarizing liquid delivery rate can be reduced, for example toaccommodate a reduced number of substrates 212, without inadvertentlyallowing the temperature of the planarizing surface 242 to drop below atemperature at which the waste matter accumulations 264 soften and/orbecome more soluble in the planarizing liquid, and/or a temperaturewhich is approximately the glass transition temperature of materialcomprising the polishing pad 240. Such a temperature drop may cause thewaste matter accumulations 264 to harden, making the polishing pad 240more difficult to condition and reducing the ability of the pad toplanarize the substrates 212 effectively.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except by the appended claims.

1. A method of controlling a selected temperature of a planarizingsurface of a polishing pad used in planarization of a substrate,comprising controlling the selected temperature of the planarizingsurface to be at least approximately 98% of a glass transitiontemperature of the polishing pad material in the polishing pad byelectrically heating a support surface supporting the polishing pad. 2.The method of claim 1 wherein the act of electrically heating a supportsurface supporting the polishing pad includes the act of heating thesupport surface under a polyurethane pad with a glass transitiontemperature of approximately 311.deg. K.
 3. The method of claim 1wherein the act of controlling a selected temperature of the planarizingsurface includes the act of elevating the temperature of the planarizingsurface to be within the range of approximately 305.deg. K. to about319.deg. K.
 4. A method of controlling a selected temperature of aplanarizing surface of a polishing pad used in planarization of asubstrate, comprising controlling the selected temperature of theplanarizing surface to be at least approximately 98% of a glasstransition temperature of the polishing pad material in the polishingpad by controlling an air temperature of air proximate to theplanarizing surface.
 5. The method of claim 4 wherein the act ofcontrolling the air temperature of air proximate to the planarizingsurface includes the act of controlling the air temperature of airproximate to a polyurethane pad with a glass transition temperature ofapproximately 311.deg. K.
 6. The method of claim 5 wherein the act ofcontrolling a selected temperature of the planarizing surface includesthe act of elevating the temperature of the planarizing surface to bewithin the range of approximately 305.deg. K. to about 319.deg. K.
 7. Amethod of controlling a selected temperature of a planarizing surface ofa polishing pad used in planarization of a substrate, comprisingcontrolling a temperature of a support surface supporting theplanarizing surface to be within the range of about 322.deg. K. to about328.deg. K. by electrically heating a support surface supporting thepolishing pad.
 8. The method of claim 7 wherein the act of controlling atemperature of a support surface includes controlling the temperature ofa support surface supporting a polyurethane pad having a glasstransition temperature of approximately 311.deg. K.
 9. The method ofclaim 8 wherein the act of controlling a temperature of a supportsurface includes elevating the temperature of the planarizing surface tobe within the range of approximately 305.deg. K. to about 319.deg. K.10. The method of claim 8 wherein the act of controlling a temperatureof a support surface includes elevating the temperature of theplanarizing surface to be at least approximately 98% of a glasstransition temperature of a polishing pad material in the polishing pad.11. A method of controlling a selected temperature of a planarizingsurface of a polishing pad used in planarization of a substrate,comprising controlling a temperature of the planarizing surface to be atleast approximately 98% of a glass transition temperature of thepolishing pad material in the polishing pad by electrically heating thepolishing pad.
 12. The method of claim 11 wherein the act ofelectrically heating the polishing pad includes the act of heating apolyurethane pad with a glass transition temperature of approximately311.deg. K.
 13. The method of claim 12 wherein the act of controlling aselected temperature of the planarizing surface includes the act ofelevating the temperature of the planarizing surface to be within therange of approximately 305.deg. K. to about 319.deg. K.
 14. A method ofcontrolling a selected temperature of a planarizing surface of apolishing pad used in planarization of a substrate, comprisingcontrolling a temperature of the planarizing surface to be at leastapproximately 98% of a glass transition temperature of the polishing padmaterial in the polishing pad by controlling a temperature of aconditioning disk positioned adjacent the planarizing surface andmovable relative to the planarizing surface.